Preparation of amide chiral stationary phase containing chiral amine for high performance liquid chromatography and enantioseparation of amino acid derivatives

A chiral selector which containing two chiral centers was prepared by condensation of (R)-1-phenyl-2-(4-methylphenyl) ethyl amine with L-Isoleucine. The N-(Boc)-isoleucine was reacted with (R)-PTE usingDCC as condensing agent in dry tetrahydrofuran at 0 degrees C for 2 h and then at room temperature for 15 h. The insoluble byproduct was filtered. The filtrate was concentrated in vacuum, diluted with methylene chloride and washed with 5% HCl solution, saturated aqueous NaHCO,, and saturated NaCl. The organic phase was separated, dried over anhydrous Na2SO4 overnight. The Boc group was subsequently cleaved with trifluoroaeetie acid to afford the chiral selector. The chiral selector was covalently bonded to aminopropylsilica gel for preparation of the chiral stationary phase using suceinic anhydride as connecting spacer. The chiral stationary phase was applied to the enantioseparation of amino acid derivatives by HPLC using n-hexane/isopropanol as mobile phase. The effect of the concentration of isopropanol in mobile phase on enantioseparation was investigated. The results showed that the chiral stationary phase possessed the enantioselectivity to amino acid derivatives. When the concentration of isopropanol in mobile phase was 1%, the baseline resolutions of Nbenzamide-o-methyl ester derivatives of leucine and phenylalanine were obtained. When the concentration of isopropanol in mobile phase was 20%, the baseline resolutions of N-3, 5-dinitrobenzamide-o-methyl ester derivatives of leucine, nor-valine, alanine and glutamic acid derivatives were obtained.